Automatic telephone system



Sept. 10, 1929.

J. E. GARDNER AUTOMATIC TELEPHONE SYSTEM Original Filed Jan. 27. 1922 3 Sheets-Sheet l Imren ur Juhn EEar'dneP PUT y:

P 1929' J. E. GARDNER 1,727,593

AUTOMATIC TELEPHONE SYSTEM Original Filed Jan. 27. 1922 3 Sheets-Sheet 2 Q Q N 1m Jul-m5 Earduer' Sept. 10, 1929. J. E. GARDNER AUTOMATIC TELEPHONE SYSTEM Original Filed Jan. 27. 1922 5 Sheets-Sheet 3 liIlll M m wmm ET w MM W wH -v INIQIIIIIIIW Nfiw Patented Sept. 10, 1929.

UNITED STATES PATENT. OFFICE.

JOHN E. GARDNER, OF CHICAGO, ILLINOIS, ASSIG-N'OR, BY MESNE ASSIGNME NTS, TO

AUTOMATIC ELECTRIC INC., OF CHICAGO, ILLINOIS, A CORPORATION OF DELA- WARE.

AUTOMATIC TELEPHONE SYSTEM.

Original application filed January 27, 1922, Serial No. 532,159. Divided and this application file January 17, 1927.

The present invention relates in general to automatic telephone systems, but is more particularly concerned with small exchanges of the type which are commonly used for giving telephone service in factories, commercial establishments and the like; and the object of the invention, broadly stated, is the provision of a private automatic exchange system embodying new features and novel 10. circuit arrangements which are better adapted to meet the service requirements of systems of this character.

A feature of the invention relates to the provision of an improved large capacity rotary connector switch having two sets of wipers with only a single test wiper per set by means of which the connector is capable of simultaneously testing for an idle line in two levels of a group of private automatic exchange lines.

This application is a division of my application Serial No. 532,159, filed January 27, 1922 and maybe considered as an improvement on Pat. No. 1,597,784, issued Aug- 2 ust- 31, 1926 to John E. Gardner.

There are other objects of the invention not now specifically mentioned which to gether with the foregoing will be described fully hereinafter reference being had to the 30, accompanying drawings forming a part of this specification.

Referring now to the drawings comprising Figs. 1, 2, and 3, there is shown by means of the conventional circuit diagrams enough of the apparatus to fully illustrate the invention. This apparatus includes a large capacity rotary connector switch H, Fig. 1, in the main exchange, a trunk line comprising conductors 140 and 141 extending to the private automatic exchange, a

cord circuit 0, Fig. 2,,a connector switch H, Fig. 3, and a subscribers station A in the private branch exchange.

Referring now more particularly to Fig.

1, the connector switch H is of the same gen eral mechanical construction as that of the well known Strowger switches, but differs from them inasmuch it is provided with an extra set of wipers and associated bank contacts; thus the connector H, which has Serial No. 161,509.

twenty levels, has access to 200 lines and is capable of testing, after selecting a group of lines, for an idle line in two levels simultaneously. One of the trunk lines extending to a private automatic exchange to which the connector switch H has access is shown in the drawings terminating in the bank contacts 106408, inclusive.

This trunk line is of the two way type, that is, is adapted to be used for calls from themain to the branch exchange or from the branch to the main exchange. In order to enable a call to be extended from the branch to the main exchange the trunk line comprising conductors 140 and 141 is provided with a lineswitch C in the main exchange. This line switch is the usual rotary type of mechanical construction the circuits of which have been modified in accordance with features of the invention and has access to trunk lines extending to first. selector switches in the main exchange.

The trunk line comprising conductors 140 and 141 terminates in thejack J, Fig. 2, in the private automatic exchange. This trunk line also terminates in multiple bank contacts in the outgoing levels of the local connector switches. This arrangement is not shown in the drawings but is well known and need not be described, it being sufficient to say that the conductors 169-471, inclusive, associated with the trunk line comprising conductors 14:0 and 14:1 extend'to the local connector selector repeater switches and are multiplied therein in the usual manner.

At 0, Fig. 2, is shown a cord circuit at the attendant operators position in the private automatic exchange. This cord circuit is one of a plurality located at the attendant opera tors position which is used for extending in-' coming calls from a main exchange to a branch exchange subscriber.

The jack J is the terminal of a trunk line extending to an incoming connector switch which is shown at H, Fig. 3.

The connector H is of the usual Strow ger type having access to local subscribers The substation A is of the well known automatic type having the usual talking inlines such as that of the substation A.

strumentalities and impulse sending device, the associated line of which terminates at the exchange in the line switch C.

The line switch C is of the well known rotary type in which the wipers have no norscriber in. the main exchange desires to ex* tend a connection to a subscriber A in the private automatic exchange. It will be assumed further that the subscriber in the main exchange has'removed his receiver and operated his calling device in order to cause the operation of his'individual line switch and the necessary number of selector switches in the main exchange to extend the connection to the trunk line terminating in the connector H, Fig. 1, and comprising conductors 10-12, inclusive. I

[As soon asthe connection is extended to the connector H theline relay 16 thereof is energized over the two sides of the calling subscribers line in series and, upon operating, closes the circuit of its associated slow acting relay 17. Relay 17, upon energizing, at its armature 87 places ground upon conductor 51 in the connect-or H in order to pro vide a locking circuit for certain relays which become operated subsequently, at its armature 39 opens a point in the circuit of the releasemagnet 102, at the front contact .of this armature prepares the impulsing circuits of the connector H and at armature 38 places ground "upon the release trunk conductorll thereby establishing in the usual manner a holdingcircuit for. the previously operated switches.

a The calling subscriber may now operate his calling device for the'next digit of the desired number thereby producing a series of interruptions in the circuit of the line relay 16 whichjretracts itsarmature a plurality of times in response thereto. At the first retract-ion of its armature an impulse of current is sent over a circuit extending from ground by way of, armature 52 and its back contact, armature 39 and its front contact, off normal springs 41 and 40, through the winding of the slow acting low resistance relay 18,and thence through the winding of the vertical magnet 101 to battery. The above is the circuit over which the first impulse to the vertical magnet is transmitted, however, upon the first vertical step of the switch the off normal springs are shifted and the remainingivertical magnet impulses traverse a 'difierent circuit which is the same as the one previously traced except that it includes the 05 normal springs 41 and 42 and armature 4E3 and-tits front contact, relay 18 being now in an operated position. The vertical megnet 101 operates to raise the switch shaft carrying the two sets of wipers 103105, in elusive, and 109-111, inclusive, step by step until these wipers stand opposite the levels of bank contacts corresponding to the digit dialled. The slow acting relay 18 energizes in series with the vertical magnet and maintains its armature attracted throughout the ver tical operation of the switch. At the termination of the vertical operation relay 1S deenergizes and transfers the impulsing circuit to the rotary magnet 98. U

The calling subscriber, upon operating his calling device for the next and final digit of the desired number, causes the line relay 16 to retract its armature a number of times corresponding to the digitdialled. At each retraction of its armature 52 an impulse of current is sent over the following path: from ground through the said armature and its back contact, armature 39 and its front contact, off normal springs 41 and 42, arma-- ture 43 and its back contact, back contact and armature 66, through the winding of the slow acting relay 27, armature 91 and its back contact, and through the winding of the rotary magnetv 98 to battery. The rotary magnet 98 operates to rotate the switch shaft carrying the two sets of wipers into engagement with the proper sets of bank contacts in which terminate the first two trunk lines extending to the desired private automatic exchange which we, will assume are the bank contacts 106-108, inclusive, and 112-114, inclusive. The slow acting relay 27 is energized in series with the rotary magnet and at its armature 7 2 closes the circuit of the slow acting relay 29, at its armature 71 short circuits the armature 66 and its back contacts on the busy test relay 26 so as to prevent the rotary magnet circuit being interrupted by a premature energization of relay 26 while the switch wipers are rotating over busy contacts, and at its armatures 69 and 70 opens certain points in the automatic rotary testing circuitwhich will be described fully later. The slow acting relay 29, upon operating, at its armature 80 closes the circuit of the slow acting relay 28, at its armature 79 opens a point in the circuit of the upper winding of switch; ing relay 30, at the front contact of this armature connects the test wiper 10a associated with the upper set of bank contacts to the test relay 26, at its armature 78 opens a point in the circuit of relay 20 and at its armature 77 prepares a point in the testing circuit of the test wiper 110 associated with the second set of wipers. The relay 28, upon energizing,at its armature 76 opens a point in the busy signalling circuit, at its armature 73 opens a point in a circuit of prepares points in the automatic rotary testing circuits.

At this point it will be convenient to explain how the lines of a group are connected in the bank contacts of the rotary connector switches so as to enable these switches to select idle trunk lines in the group after having connected therewith. On all lines over which it is desired that the connector switch rotate if theline is busy the connection of the normal conductors extending from the lineswitch to the connector banks are reversed. This may be seen by refer ring to the connection of the normal con 1 ductors extending from the line switch C to the bank contacts 106108, inclusive. That is the conductor 141 which extends from ground in the lineswitch C is connected to bank contact 106 instead of bank contact 108 and the conductor 140 which is connected to battery in the lineswitch C extends to contact 108 instead of contact 106. The line switches associated with all the lines which are the end of the group in the rotary connector are changed so that a resistance appears in the private normal conductor as may be seen with reference to the lineswitch C, that is the connection between the terminals 135 and 136 which normally short circuits the resistance R and also the connec tion which normally short circuits the resistance R are removed. These resistances are of about 300 ohms each and are included in the circuit so that should this line be making, a call ground will appear on the private normal conductor through this resistance and if a rotary connector switch 1S rotated into engagement with the bank con tacts associatedwith this line the rotation of the switch will cease and a busy tone will be given to the calling subscriber.

Advertinq, now to the operation of the connector H when engagement is made with the bank contacts 106-108, inclusive, it will be assumed that the first trunk line or" the group, which is the trunk line now associated with the first set of wipers 103-105, inclusive, is lousy. Under these conditions there will be a Q IOUHCl potential on the test contact 107 and. the test relay 26 will be energized over the following circuit: grounded, test contact 107, test wiper 104, armature 79 and its front contact, armature 90 and its back contact, and thence through the winding of the test relay 26 to battery. Relay 26, upon energizing, at its armature prepares a point in its locking circuit which is established immediately upon the deenergization of the slow acting relay 29, at armature 66 opens a point in the circuit of the rotary magnet, at armature 67 prepares a point in the circuit of switching relay 31, at armature 68 prepares a po nt in the busy signalling lead, at its armature 64 switches the connection of the testrelay 20 from the first set of wipers to the second set for a purpose which will appear later and at its armature 63 closes a point in the circuit of the test relay 25. Assuming); that the second trunk line of the group busy a ground potential will be present on the test contact 113. A circuit for the testing relay 25 may now be traced from grounded test contact 113, test wiper 110, armature 77, and its front contact, armature 63 and its front contact and through the winding of relay 25 to battery. Relay 25, upon energizing, at its armature 59 prepares a point in its locking circuit which is completed immediately upon the deenergization oi the slow acting; relay 29, at its armature 62 opens a point in the circuit of switching relay 31, at armature 284 transters the circuit of the slow acting relay 17 to ground at armature 283 for a purpose which will be explained later,and at armatures 60 and 61 closes two points in the automatic rotary testing circuit. Immediupon the deener 'ization of the slow a ting relay 2?, a circuit for the both wind of the stepping relay 21 may be traced, the circuit of winding 24 extending from grounded test contact 107, test wiper 104, arn'iaturc and its front contact, armature 70 and. its back contact, armature 61' and its front contact, armature 100 and its back contact, througrl'i the winding of the coil 24 and the resistance R to battery. and the circuit of winding 23 extending from grounded test contact 113, test wiper 110,- armature 74 and its :r'ront contact, armature 69 and its back contact, armature 60 and its front contact, armature 99 and its back contact and through the winding of the coil 23 and resistance R to battery. The relay 21 is energized over this circuit and, upon operating, at its arinatures 56 and 57 cstablishes locking circuits for both its windings 23 and 24, at armature 58 closes the circuit of the rotary magnet 98. Magnet 98 operates to rotate the switch shaft carrying the two sets of switch wipers into engagement with the next two sets of bank contacts and at its armatures 99 and 100 opens the locking circuits of the coils 23 and 24 of the stepping relay 21. Relay 21 deenergizes thereby opening the energizing circuit of the rotary 'magnet which deenergizes also. It will be noted that when an impulse of current is sent to the rotary magnet 98 the slow acting relay 29 will receive an impulse of current. Therefore, the slow acting relays 29 and 28 will remain energized to preserve the continuity of the testing ci.r--

cuits.

At this point it is convenient to describe .sistance of 300 ohms.

attract its armature with only one coil energized as the relay armature is short c1rcuited by the soft lron core of the other 0011.

However, it will be apparent that when both coils 23 and 24 are energized magnetic flux must flow in a path which includes the relay armature which will thus be attracted. The windings 23 and 24- of the coil 21 are of very low resistance (about 5 ohms) and are in series with resistance coil R which is of somewhat higher resistance (about 50 ohms). The relay is wound in'this manner so that if there happens to be a ground potential upon the test contacts through a. fairly high resistance say of about 300 ohms, which is the case when the connector wipers engage a busy line which is the last trunk line of the group, it will not be energized. That is, the relay 21 does not attract its armature with one coil energized by a test contact which is directly grounded and the other coil is energized over a circuit which in, cludes a test contact grounded through a resistance otabout 300 ohms. It will be observed that under these conditions the winding of the coil energized through 300 ohms is practically short circuited by direct ground through one of the low resistance windings of the relay 21. There is practically no margin to the adjustment of the relay 21 inasmuch as under these conditions which are the most adverse encountered the coil energized through 300 ohms generates practically no magnetic flux and the flux generated by the other coil is short circuited from the relay armature so that it does not operate.

Returning now to the trunk selecting operation of the connector switch H, if the next two trunk lines, whichare now associated with both sets of Wipers, are rotary trunks and busy, the relays 25 and 26 will be maintained energized and the stepping relay 21 will again operate to close the circuit of therotary magnet 98. The alternate operation of the stepping relay 21 and the rotary magnet 98 continues until the switch wipers arerotated into engagement with an idle trunk line or a busy trunk line which is the last one of a group. It will be noted that each impulse sent to the rotary magnet 98 also keeps the slow acting relay 29 energized so that the test wipers are maintained connected to their respective testing relays.

Assuming that the upper set of wipers en-- gage a trunk line which is-the last of a group ground will be connected to the test contact engaged by the test wiper 104 through a re- This resistance is included in the private normal circuit as will appear fully later. Relay 26 will be maintained energized but the stepping relay 21 will not operate for the reasons stated above .and the rotation ofthe connector switch will cease. The slow acting relays 28 and 29 deenergize and a busy tone is given to the calling subscriber over a circuit extending from the busy machine, back contact and armature 76, front contact and armature 68 to the lower line conductor 12 and thence over the calling subscribers line. Upon hearing this signal the calling subscriber will replace his receiver thereby initiating the release of the operated switches including the connector H in a manner which will be described subsequently. A here the last trunk line of the group terminates in. a set of bank contacts engaged by the upper set or" wipers 103-105, inclusive, it is necessary to leave the bank contacts associated with the lower set of wipers open and to ground the test contact of this set in order to secure proper operation of the connector H. However, Where there are an even number of trunk lines in the group the last trunk line will terminate in a set of contacts accessible to the lower set of wipers and in this case no special provision is necessary. That is, it is unnecessary to leave any set of bank contacts disconnected from trunk line. In order to describe the operation in this case it will be assumed that the connector Hrotates its wipers 109111, inclusi e. into engagement with the trunk line which is the last of a group. The operation in this'case is similar to that above described, that is, the relay 26 remains energized as does the relay 25, the relay 21 remaining inoperative. As relay 21 does not energize the rotation of the switch ceases and a busy signal is given to the calling subscrlber.

It will now be assumed that the connector H is rotated until its upper set of wipers are associated with an idle trunk line in the group. Under these conditions there will be no ground potential present upon the test contact engaged by the test wiper 104. Relay 26 deenergizes and opens the circuit of the test relay 25. Then immediately upon the deenergization of the slow acting relay 29 a circuit is completed extending from ground on release trunk conductor 11, armature 65 and its back contact, through the upper winding of the switching relay 30, back contact and armature 96, back contact and armature 7 9, test wiper 104, test contact associated with it, and thence over the private normal conductor thereof through the winding of the switching relay in the associated line switch and motor magnet to battery. The relay 30 is energized over this circuit, and, upon operating, establishes a locking circuit for itself at its armature 88, opens a point in the circuit of the testing relay 26 at armature 90, opens the rotary magnet circuit at armature 91, at armature 89 places direct ground upon the testwiper 104, at armature 87 prepares a circuit for giving the calling subscriber the so called ringing inell) duction and at armatures 86 and 92 completes the ringing circuit. Ringing current is now projected out on the trunk line until a response is obtained. Other results of the energization. of relay 30 are that at armature 283 ground is removed from armature 284 for a purpose which will be described, and at armature 285 a locking circuit is prepared for the relay 25.

The above is the operation of the connector H when an idle rotary line is connected with. However, it the idle line engaged by the upper set of wipers is the last trunk line in the group the operation is slightly dilierent. This will now be briefly described. It will be noted that upon the deenergization ofthe slow acting relay 29, when a circuit is completed for the switch ing relay 30, a circuit is prepared which extends ;trom battery through the winding of relay 20, normallyclosed springs controlled by armature 4L8, armature 64: and its back contact, armature 78 and its back contact, back contact and armature 92, armature 97 and its back contact, to wiper 105. Ithas been described before how the normal conductors extending from the lineswitch are reversed in case the line is a rotary line and how if the line is straight they are connected in the usual manner. As it is assumed that the upper set of Wipers are now in engagement with a trunk line which is the last of the group there will be ground on the bank contact engaged by the wiper 105 from the back contact of an armature in the associated line switch such as the armature 129 in the lineswitch C. The relay is therefore energized, and upon operating, at its armature 48 establishes a locking circuit for itself,

at its armature 49 removes direct ground from the armature 89 on the switching relay and at its armatures 47 and 50 reverses the connections between the wipers of: the connector and the connections to the ring cut oil and back bridge relays 19 and 15, re- 1=-:pecti*.*ely. Upon the energization of the switching relay 30 which occursin the same manner as before described, ground is placed upon the test contact engaged by the test wiper 104, through the resistance R which is of about 300 ohms. The other circuit changes brought about by the energization oi the switching relay 30 are the sameas before described except that ringing cur rent is now sent out over the wipers of the connector H in the opposite direction. This is for a purpose which will appear fully later. i

Should the lower set of wipers of the connector H have been the first to engage an idle trunk line the operation of the connector differs from that above described in e following manner: The test relay 26 associated with the upper set of wipers re mains energized while the test relay 25 de-' energizes. Under these conditions the rotation oi the switch'is' stopped and immediately upon the deenergization of the slow acting relay 28 a circuit is" completed eX-- tending from ground by way of front contact and armature 67, armature 62 and its back contact, through the upper winding of the switching relay 31, back contact and armature 74, test wiper 110i associated with the lower set of wipers, test contact engaged thereby and thence over the private normal conductor through the switching relay and motor magnet oi the associated line switch to battery. The switching relay 31 is energized over this circuit and, upon operating, establishes a locking circuit for itself at armature 94:, at this same armature closes a circuit for the lower winding oi the switching relay 30, at armature 95 places ground upon the test contact engaged by the test wiper 110, at armature 96 opensa point in the circuit of the upper winding of relay 30 and at armatures 93 and 97 disconnects the first set of wipers and connects up the second set. The energization of the switching relay 30 produces the same results as before except that ground is disconnected from the armature 89 so that the wiper 104: will remain disconnected, from the switch. In the above operation, upon the deenergization of the slow acting relay 28, the discriminating relay 20 is con, nected with the wiper 111 of the lower set of wipers in order to test whether or not the associated line is the last one of a group, relay 20 is energized and operates as before described, that is, upon the energization of the switching relays 30 and 31 ringing current will be projected in 'the'oppo'site direction from the wipers of the connector and ground will be supplied by thetest'conta'ct engaged by theltest wiper 110 through the resistance B so that if another'connector is rotated into engagement with this line its rotation will be stopped and a signal given to thecalling subscriber.

Returning, now'to the, description of the extension of the connection it will be as .sumed that when the connectorH was operated into engagement with theibank contacts 106-108, inclusive, the, associated line was idle. Under these conditions the relay 26 is not energizedand immediately following the deenergization of the slow acting relay 29 the discriminating relay 20 is and the circuit or the switching relay30 is closed at armature 79. As the bank contacts 106-108, inclusive, are associated with the first line of a group extending to the private automatic exchange the connector switch must rotate over it'when it is busy and therefore, the normal conductors will be connected'in thereverse mannerand the discriminating relay 20 will not be ener inc .121) connected to the wiper, 105 at armature 78 40 ity to that normally supplied by the line versed thereover.

gized as the contact 108 is connected to battery in the line switch G. Switching relay 30 is energized over the following circuit:

- armature 79, test wiper 104, test contact 107, through the winding of the switching relay 121 and the motor magnet 125 of the line switch C to battery. Relay 121 is energized over this circuit. However, its operation at this time is only effective to open its back contacts but not to close its working contact on account of a mechanical interlocking device controlled by the armature of the line relay 123 which is now normal. The operation of relay 121 disconnects the normal battery and ground connections in the lineswitch G from the trunk conductors 140 and 141.

In the connector H relay 30, upon operating, makes certain circuit changes in a man nerwhich has already been described, these being among others: ground is placed upon thetest contact 107 and the ringing circuit is closed. Ringing current is now 1Ilte1I111l3 tently projected over the trunk line comprising conductors 140 and 141 extending to the private automatic exchange. It will be noted that ringing current leaves the wiper 103 and returns to the wiper 105. The oper ation of the relay 121 in the liueswitch C, as beforestated, removes the normal battery connection from the trunk line comprising conductors 140 and 141. Since the conductors 140 and .141 are reversed in the bank contacts of the connector in the battery supplied by the connector H superimposed on the ringing current is of the opposite polarswitch C when the trunk line is not in use. The relay 152 in the trunk circuit associated with this trunk line at the private automatic exchange is a high resistance polarized relay normally energized by battery on the trunk in series with the windings of the line relay 123 and the relay 122 and consequent ly it will retract its armature 165 whenever battery is removed from the trunk orre- Thus as soon as the trunk line is seized by the connector H the relay 152 will retract its armatureJ Upon deenergizing, relay 152 completes a circuit extending from ground by way of back contact and armature 162, armature 165 and its resting contacts and thence through the winding of the slow acting relay 153 to battery. Upon energizing, this latter relay at armature 167 places ground upon the release trunk conductor 170 extending to multiple test contacts associated with this trunk line in the outgoing level of the local connector switches thereby making this trunk line busy to any outgoing calls'and at armature 173 prepares a point in its locking circuit. The relay 150 in this trunk circuit is bridged across the conductors 140 and 141 in series with a condenser and is operated by the ringing current from the connector H. Relay 150, upon energizing, establishes a look ing circuit for itself at its armature 161 and at its armature 160 closes the circuit of the line lamp L. Upon noting this signal, the attendant operator will insert the plug of an idle cord circuit, which we will assume is the plug P of the cord circuit 0, into the jack J. By this operation a circuit is completed extending from ground through the winding of the low resistance relay 175, normally closed springs controlled by armature 181-, sleeve of plug P, sleeve of jack J and through the winding of relay 151 to battery. The relays 175 and 151 are energized over this circuit. Relay 151, upon operating, at its armature 163 opens the locking circuit of the ring up relay 150, at its armature 164 removes the polarized relay 152 as well as the lower winding of the ring up relay 150 from bridge of the trunk conductors 140 and 141 and at its armature 162 removes one ground connection from the armature 165 of the polarized relay. This latter operation is ineii'ective at the present time as ground has been connected to the armature 165 by the operation of spring 155 of jack J. The visual signal 168 is energized in multiple with relay 151. However, its operation is without function at the present time. In the cord circuit 0, relay 175 at its armature 180 closes the circuit of the polarizing winding of the electro polarized relay 177 and also the circuits for the supervisory lamps L andL It will be noted that the lower winding of the polarized relay 177 is bridged directly across the cord circuit and consequently across the trunk line comprisng conductors 140 and 141. The ring out off relay 19 in the connector H is therefore energized in series with the lower winding of relay 177. Upon operating, relay 19 establishes a'locking circuit for itself at armature 45, at armatures 44 and 46 opens the ringing circuit and at the front contacts of these armatures connects up the back bridge relay 15. Back bridge relay 15 is also energized over the trunk line and upon operating, reverses the normal current flow over the incoming trunk lines comprising conductors 10 and 12 for supervisory or metering purposes, Another result of the energization of relay 15 is that a circuit is closed at armature 32 for the slow acting relay 33. Upon operating, the latter relay at armature 34 prepares a circuit for the relay in order to prepare a release circuit for the connector which will be explained hereinafter. In the cord circuit O the electropolarized relay 177 is energized in series with the ring cut off relay 19 as the current flow from the (ill connector H is in the proper direction to operate it. Upon operating, relay 177 at its its armature 186 opens the circuit of the supervisory lamp L and at its armature 187 closes the circuit of the slow acting relay 178. Relay 178, upon operating, prepares a circuit for the relay 17 6 at armature 183. The attendant operator will now throw the listening key K thereby associating her head set with the cord circuit and enabling her to ascertain what number the calling subscriber in the main exchange desires. Should the attendant operator plug into the jack J with the listening key K thrown she would likely get a ring in the ear were not special provisions made to prevent this. If ringing current is being impressed on the trunk line when the operator plugs in the jack J with the key K operated the alternating current relay 192 associated with her head set would be energized. Upon operating, relay 192 at armature 193 short circuits the right hand winding of the repeating coil through the resistance 194-. This prevents any disagreeable noises in the operators head set due to the ringing current. lVhen the attendant operator finds out what numher is desired she will insert the plug P into an idle jack which we will assume is the jack J extending to the incoming connector switch H, Fig. 3. By this operation a circuitis completed for the line relay 210 of the connector H over the following path: from ground by way of normally closed. springs controlled by armature 191, impulse springs of the calling device CD, springs of the release key K", spring 196 and its working contact, sleeve of plug P, sleeve of jack J, springs 198 and .199, conductor 201 and through the winding of the line relay 210 of he connector Hto battery.

The relay 210 is energized over this circuit and, upon operating, closes the circuit for its associated slow acting release relay 211. Upon operating, the latter relay opens the release magnet circuit at armature 229, at the front contact of this armature pre-' pares the operating circuits of the conncc tor H and at armaturcs 227 and 228 prepares certain circuits for other relays in the switch.

It will be noted that the line relay 210 is not connected directly to the sleeve of the jack J but is connected through the springs 19S and 199. The connection is made in this manner so that there will be no so called preliminary impulse sent to the line relay 210 due to contact being made between the tip of the plug P and the sleeve of the jack J while the plug is being inserted into the said jack. Ground is present on the tip of the plug P being supplied by the winding of the back bridge relay of the connector H in the main exchange. By this arrangement no impulses-will be sent to the line relay 210 until the operator operates her calling device.

The attendant operator may now operate the calling device CD in accordance with the first digit of the desired subscribers number thereby producing a corresponding series of interruptions in the above traced circuit of line relay 210 whichdeenergizcs a plurality of times in rcsponseqthereto. At the first retraction of its armature 226 a circuit is completed extending from ground by way of the said armature and its back contact, armature 229 and its front contact, off normal springs 231 and 230 through the winding of the vertical magnet 219 and then through the winding of the slow acting relay 213 to battery. The above is the circuit over which the first impulse to the vertical magnet is transmitted. Upon the first vertical step of the shaft the off normal springs are shifted and the remaining vertical magnet impulses are sent over a circuit which is different from the one previously traced inasmuch as it includes the off normal springs 231 and 232, and armature 236 and its front contact, re lay 213 being now in an operated position. Magnet 219 operates to raise the switch wipers 258261, inclusive, step by step until they are placed opposite the level of bank contacts in which is located the terminals of the substation A. The slow acting relay 213 which is energized in series with the vertical magnet maintains its armature attracted throughout the vertical movement of the switch and at its termination retracts its arinatures and transfers the impulsing circuit to the rotary magnet 220. 7 The private automatic exchange operator may now operate her calling device in accordancewith the final digit of the called subscribers number. As before, a series of.

interruptions is produced in the circuit of line relay 210 which deenergizes a plurality of times in response thereto. Upon each deenergization, a circuit is completed extending from ground by Way of armature 226 and its back contact, armature 229 and its front contact, off normal springs 231 and 232, armature 236 and its back contact, back contact and armature 246, through the winding of the slow acting low resistance relay 216. armature 256 and its back contact, and thence through the winding of the rotary magnet 220 to battery. Magnet 220 operates to rotate the wipers '258.,261, inclusive, into engagement with the bank contacts associated with the line of the desired called substation A which we will assume are the bank contacts 262265, inclusive. The slow acting relay 216 is energized in series with the rotary magnet and operates to connect the testwiper 260 to the test, relay 215. If the desired subscribers line should be busy at this time a ground potential will be found on the test contact 264. A-circuit may then be traced extending from the said ground test contact by way of test wiper 260, armature 250 and its front contact and through the winding of the test relay 215 to battery. Relay 215 energizes over this circuit and operates to establish a point in its locking circuit at armature 245, this being completed upon the deenergization of the slow acting relay 216, at armature 246 opens the circuit of the rotary magnet, at armature 247 prepares an automatic testing circuit which will be described later and at armature 248 places a busy tone on the lower heavy talking conductor 202. This tone will be audible to the attendant operator and the calling subscriber and will serve to inform them that the desired line is busy. Should the calling subscriber in the main exchange now desire a connection with another subscriber in the private automatic exchange he may inform the attendant of this fact. The attendant operator will then operate the release key K thereby opening the circuit of the line relay 210 of the connector H. lVhen thisrelay deenergizes the slow acting release relay 211 deenergizes shortly after and the connector H is released in the well known manner. The operator may now, by operating her calling device for the digits of the desired subscribers number cause the connector H to connect with the desired line. The operation in this case is similar to that just described and will be readily apparent. However, should the calling subscriber in the main exchange replace his receiver upon hearing the audible busy signal the connection will be released in a manner which will be described hereinafter.

'It will now be assumed that the line of the substation A isv idle when the wipers of the connector H are rotated into engagement with the bank contacts262 265, inclusive. Under these conditions there will be no ground on the test contact 264 and the test relay 215 isnot operated. Then,following the deenergization of the slow acting relay 216, a circuit iscompleted extending from ground by way of front contact and armature 228, normally closed springs controlled by armature 235, armature 245 and its back contact, through the lower winding of the switching relay 217 back contact and armature 250, test wiper 260, test contact 264, through the winding of the switching relay 266 and motor magnet 267 of the line: switch C to battery. The relays 217 and 266 operate over this circuit. However, due to a mechanical interlocking device controlled by the armature of t-h line relay 268 which has not been energized, the switching relay 266' only attracts its armatures enough to disconnect the line of the substation A from its normal battery and ground connections in the lineswitch C. r

e In the connector H, the switching relay 217 ,upon energizing, establishes a locking circuit fo 1 itself at its armature 254, places ground upon the test wiper 260 at armature 255, opens the rotary magnet circuit at armature 256 and at armatures 252 and 257 completes the ringing circuit.

Having completed the desired connection the attendant operator may now restore the listening key K nect-s her heat set from the connection and enables her to attend to other calls. By the restoration of key K the circuit of the line relay 210 of the connector H is transferred to ground through the springs 195 and armature 197 of relay 176 and its back contact for a purpose which will appear subsequentl In the connector H, ringing current is now intermittently applied to the line of the substation A until an answer is obtained. v 'fhen this occurs a circuit is completed over the called subscribers line for the ring cut oil relay 21%. Upon energizing, this relay establishes a locking circuit for itself at armature 238, at armatures 237 and 239 opens the ringing circuit and at the front contactofthese armatures finally completes the talking connection.

When the ring out off relay 9.1a energizes a direct metallic circuit extends from the back bridge relay of the connector H in the main exchange to the substation A. The current lowing over this circuit serves to ener ize the relay 179 in the cord circuit 0. Relay 179, upon energizing, opens the circuit of the called supervisory lamp L thereby notifying the attendant operator that the called subscriber has answered and closes the circuit of the slow acting relay 280 at armature 2S2. Upon operating relay 280 prepares a circuit for relay 176 at armature 281. The conversation may now be carried on over the heavy talking conductors between the subscriber in the main exchange and the subscriber at substation A, battery being supplied to the subscriber in the main exchange from the windings of the. line relay 16 of the connector H and to the called subscriber at substation A in. the private autoatic exchange from the windings of the back bridge relay 15 of the connector H.

At this point it will be convenient to describe the operation of the local connector l. when it operates to select an idle line in a group, of lines. in order to arrange the connector H to give this class of service two test wipers are provided. In order to enable the switch to discriminate between private and rotary busy lines the test contacts of the latter engaged by the two test wipers must be tied together and those of the last trunk line in the group or those of private lines left open. Assuming that the connector H is rotated into engagement with such a group of lines and that the first line This operation discon thereof is busy. Under these conditions there will also be a ground potential on the test contact engaged by the test wiper 259 as well as the test wiper 260. A circuit is now completed extending from the grounded test contact engaged by the test wiper 259, over said test wiper, back contact'and armature 2&9, armature 253 and its back contact, back contact and armature 221, armature 2 17 and its front contact, through the wind ing of the stepping relay 212 and thence through the winding of the stepping relay 213 to battery. The relays 212 and 213 are energized over this circuit. Relay 213, upon energizing, again connects the test 'iper 260 to the test relay 215 at armature 235. Relay 212, upon energizing establisl es a locking circuit for itself and relay 213 at armature and at armature completes the circuit of the rotary magnet 220. lvlagnet 220operates to rotate the switch wipers 258-261, inclusive, into engagement with the next set of contacts in the selected group, and at armature 221 opens the locking circuit of the relays 212 and 213. Upon deenergizing, relay 212 opens a circuit of the rotary magnet 220 which deenergizes also. if this next trunk line is not the last one of the group and is busy the test relay 215 will be maintained energized and the stepping relay 212 will operate as before. The alternate operation of the stepping relay 212 and the magnet 220 continues until an idle line is found or until the switch wipers are rotated into association with the last trunk line of the groin If this is busy also a test relay 215 will be maintained energized. However, no circuit will be completed for the stepping relay 212 and as ground is not present on the test contact engaged by the upper test wiper 259 the rotation of the switch ceases and a busy tone is given to the calling subscriber. In case the connector H is rotated into engagement with an idle trunk line the operation proceeds as before described.

Referring back to the description of the extension of the connection, when the con versation is terminated both the subscribers will replace their receivers upon their respective switch hooks. In order to describe the releasing operation in detail it will be assumed that the called subscriber at substation A replaces his receiver before the calling subscriber in the main exchange. VJ hen the receiver is replaced at substation A the circuit of the supervisory relay 179 in the operators cord circuit O is opened and this relay deenergizes, Upon retracting its armatures, a circuit is closed for the lamp L in order to notify the operator that the called subscriber has replaced his receiver and at armature 282 the circuit of the slow acting relay 280 is opened and before the deenergization of this latter relay an impulse of current is sentover apath extending fromground by way of the said armature and its back contact, armature 281 and its front contact, and through the wind ing of relay 17 6 to battery. Relay 17 6, upon operating, at its armature 181 disconnects ground from the sleeve of the plug 1?, at the front contact of this armature establishes an auxiliary circuit for the sleeve relay 17 5,

at armature 182 establishes a locking circuit for itself, opens the circuit ofthe line relay 210 of the incomingconnector switch H8 at armature 197 and at armatures 184 and 183 disassociates the cord circuit O from the jack J. As a result of this latter operation the circuit of the back bridge relay 15 in the connector H at the main exchange isopened.

Upon retracting its armatures relay 15 re storesthe normal flow of current over the conductors 10 and 12 of the incoming trunk line and at armature 32 opens the circuit of the slow acting relay 38. After the deenergization of relay 15 and beforethe deenergization of relay 83 an impulse of current is sent over a circuit extending from ground by wayof armature 32 and its back contact, front contact and armature 34, and through the winding of the relay 25 to battery. A circuit in multiple with the above is completed for the slow acting relay. 29. The operation of relay 29 at this time serves merely to remove one ground connection from the release trunk conductor 11. Upon energizing, relay 25 at its armature 59 es tablishes a locking circuit for itself and relay 29 to ground onconductor 51 and at armature 28% opens the circuit of the slow acting relay 17. armatures of relay 25'are without function at the present time. Upon the" deenergization of the'slow acting relay 17 ground is removed from therelease trunk conductor 11 thereby opening aholding circuit of the previously operated switches in the main exchange and the circuit of the release magnet 102 of the connector H is prepared.

Immediately uponthe deenergization of the relay 25 which takes place as soon as its locking circuit is opened by the deenergization of the slow acting relay 17 magnet 102 operates to restore the connector H to its normal position in the usual manner. I

Returning now to the description of the circuit operations in the private automatic exchange the results occasioned by the dis connection of ground from the sleeve of the plug P will now be considered. When ground is disconnected from the sleeve of plug P thecircuit of the relay 151 in the trunk equipment is opened as is the circuit of the visual 168. Relay 151 upon deenergizing, at its armature 164E again bridges the lower winding of the ring up relay 150 and the winding of'the high resistance polarized relay 152 across the trunk conductors 140 The operation of the other and 141. It will-he understood that when the connector 11 in the main exchange was released that the cut ofi relay 121 in the lineswitch C is deenergized to again connect the normal battery to the trunk conductors 140 and 141. As this battery flows in the opposite direction to that supplied by the connector H the polarized relay 152 in the trunl;

local connector switches. The two way trunk line shown in the drawings may now be used for a call in either direction even though the plug P remains in the jack J and the operator will be given full supervision in a manner which will be described subsequently. I I

It will beremembered-that relay 176 in the cord circuit 0 also opens the circuit of the line relay 210 of the incoming connector H. Upon deenergizing, this latter relay opens the circuit of the associated slow acting relay 211. Upon retracting its armatures, the latter relay opens certain looking circuits in the connector H and closes the circuit of the release magnet 218. The release magnet 218 operates to release the connector in the usual manner.

Th'eprivate automatic exchange operator upon noting the lighting of the lamp L will withdraw the plugs of the cord circuit from their associated jacks. Upon the plug P reaching its normal position the locking circuit of the relay 1? 6 is opened and this relay .deenergizes to open the circuit of the relay 17 5 and restore certain other circuits in the cord circuit to normal.

Adverting' back to the description of the extended connection it will be assumed that the calling subscriber in the main exchange is the first to replace his receiver. When the receiver is replaced'at the calling substation the circuit of the line relay 16 in theconnector H is opened. This relay deenergizes and in turn opens the circuit of the slow. acting release relay 17. Upon retracting its armatures the latter relay removes ground from the release trunk conductor 11 thereby allowingthe preceding switches to release, at armature 37 opens the locking circuit of the various relays in the connector H and at armature 39 completes the circuit of the release magnet 102. Magnet 102 operates to restore the connector H to nor mal. As soon as ground is removed from the test contactlOT associated with the trunk line comprising conductors 140 and 1&1. The cut oil? relay 121 in the line switch C retracts its: armatures thereby again connecting the normal battery to the trunk line. This battery flows in the opposite direction 'to that which has been supplied by the connector H. Current is now reversed in the lower winding of the electropolarized relay cuit of the slow acting relay 178. After the deenergization of the. polarized relay 177 and before the deenergization of the slow acting relay 178 an impulse of current is sent over a circuit extending from ground by way of armature 187 and its back contact, front contact and armature 188 and through the winding of the relay 176 to battery. Relay 176 operates in the samemanner as before to establish a locking circuit for itseli at armature 182, to open at armature 197 the circuit of the line relay 210 of the connector H, to open at armature 181 the circuit of the busy visual 168 associated with the trunk circuit and also that 01 relay 151 and at the front contact of this armature toestablish another circuit for the sleeve relay 175. Another result of the energization of relay 1'56 is that at amaturcs 183 and 184 the cord circuit is disconnected from the trunk even though the plug P remains in the jack J. As the circuit of the line relay 210 of the incoming connector H is opened the release of the connector H takes place as before described. As the circuit of the relay 151 in the trunk equipment associated with the jack J is also opened by the operation of relay 176 this relay will deenergize to again connect the lower winding of the ring up relay and the windings of the high resistance polarized relay 152 across the trunk conductors 1&0 and 141. The polarized relay 152 is immediately energized and operates to open the circuit of the slow acting relay 153. The latter relay deenergizes after a short interval and again renders the multiples of the trunk line accea 'ible in the local connector switches by removing ground from the release trunk conductor 170. The trunk line comprising conductors HO and 1 11 is now free and may be used for calls in either direction even though the plug P remains in the jack J and the ordinary supervisory call signal operates just the same as if the plug P were out of the jack.

In response to the lighting of the supervisory lamps L and L the operator will withdraw the plugs of the cord circuit from the jacks J and J before described. lVhen the plug P reaches its normal position the plug seat switch PS is operated and the locking circuit of the relay 176 is opened. Upon doe-energizing, this relay opens the circuit of the sleeve relay 175 and restores certain other circuits to normal. However, should the attendant be busy and leave the plug in the jack for some time after the operation of the supervisory signals the trunk line comprising conductors 140 and 14-1 may still be used for calls in either direction as has already been indicated. The operation under these conditions will now be described.

It the trunk line is again seized in the main exchange the polarized relay 152 is energized to busy the trunk line to the local switches in the private automatic exchange and the ringing current impressed upon the trunk line operates the ring up relay 150 in the same manner as before. he lay 150 locks itself energized and closcsthe circuit of the supervisory lamp L. Under these conditions the operator has only to operate the listening key K in order to answer the call. By this operation the cord circuit is associated with the trunk as the locking circuit of the relay 176 is opened and all circuits are now in the same condition as if the operator had answered the call by plugging into the jack.

Should the trunkline be seized for an outgoing call from the private automatic to the main exchange ground will be placed upon the conductor 170 by the local connector selector repeater thereby energizing the relay 151 of the trunk circuit in multiple with the busy visual 168. The operation of the visual 168 serves to notify the operator that the. trunk line is being used for an outgoing call. Relay 151 operates to remove the low er winding of the ring up relay 150 and the high resistance polarized relay 152 from bridge of the two trunk conductors 140 and 1/11. The line relay 123 of the line switch (1 associated with the seized trunk line in the main exchange is immediately energized via a direct current bridge in the connector selector repeater and operates to close the circuit of the switching relay 121 in series with the motor magnet 125. It will be noted that the test wiper 143 is normally connected through a back contact on switching relay 121 to a point in the above circuit midway between the switching relay and the motor magnet. Thus it will. be seen that as soon as the trunk line with which the switch wipers of the line switch C are associated becomes busy the ground potential on the test contact engaged by test wiper 143 causes the operation of the motor magnet 125. Thus it will be seen that the wipers of the lineswitch are always associated with an idle trunk line or else are being operated in search of one. That is, the rotary lineswitch C preselects its trunks.

Returning now to the operation of the line switch C when the trunk line comprising conductors 1450 and M1 was seized in the private automatic exchange the lure rev lay 123 energizes as before described and closes the circuit of the switching relay 121. The latter relay, upon operating, extends the seized trunk conductors to the line relay of the selected first selector at armatures 126 and 129, at armature 12"! opens a point in the circuit of relay 12-1 and at armature 128 prepares a holding circuit 101' itself. The subsequent operations wherein the connection is extended to the desired called line in response to the digits dialled by the calling subscriber in the private automatic exchange takes place in the usual manner.

The attendant operator sometimes finds it desirable to extend connections to the main exchange for certain subscribers in the private automatic exchange. In order to enable her to do this whenthe plug of a cord circuit is placed in the jack of an idle trunk line a calling out key such as key 5 in the cord circuit 0 is provided in all the cord circuits. The operation will now be briefly described when the. operator desires to or;- tend a call to a subscriber in the main exchange. When the operator inserts the plug or an idle cord circuit into the jacket an idle trunk line, the plug P into the jack J for exai'nple, a circuit is completed for the relay 151 over the sleeve of a cord circuit in multiple with the visual 168. Belay 151 operates to remove the ring up relay 150 and the high resistance polarized relay 152 from bridge of the trunk conductors 140 and 141 as before described. Relay 152 immediately retracts its armatures its circuit is now open. However, its operation is ineffective at the present time to close a circuit of the slow acting relay 153. The multiples of the trunk line comprising conductors 1 10 and 141 in the banks of the local connector switches are busied by ground through the winding of the low resistance relay over a circuit extending from ground through the Winding of relay 175, normally closed springs controlled by armature 181, sleeve of plug P, sleeve of jack J, back contact and armature 167 to release trunk con ductor 170. If theoperator plugs into the jack with the key K thrown the calling device CD is bridged across the conductor. 1 10 and 1 1-1. This occurs in the following manner: When the key K is operated the relay 190 is energized. Upon operating, this relay at its armature 191 bridges the calling device across the trunk circuit over the circuit extending from conductor 140, tip 01 plug P, working contact of spring 197 and the said spring, springs of release key K impulse springs of the calling device CD, front contact and armature 191, right hand winding of the repeating coil associated with the operators head set, spring 1419 of key K and its working con.- tact, ring of plug P, ring of jack J, to trunk conductor 1 11. Line relay 123 is iinniediately energized over this circuit and the line switch C operates to extend the connection to a preselected first selector switch. Should the operator plug in the jack J with the key K normal the line relay 123 ot the line switch C would be energized series with the lower winding of electropolarizing relay 1?? of the cord circuit C. l-lowever the polarized relay would not be operated at this time as the current in its polarizing winding opposes the current in its other winding, it being of course und rstood that when the plug P was placed in the J relay 175 operated to e ergize the polarized winding or relay 1?? and to light th supervisory lamps L and L in response to the digits dialled by the attendant operator in the private automatic exchange a series of automatic switches in the main exchange are operated to e3;- tend the connection to the desired called subscribers line in a well known manner. Vl hen the connection is completed the attendant operator will restore the key 1: to normal. swers the normal current flow is reversed over the trunk conductors 1 1-0 and 14:1 and the electropolarized relay 177 in the cord circuit 0 is operated to eliace the supervisory lamp L thereby notifying the attendant that the called subscriber has answered. The attendant operator will now throw the key K and inform the called subscriber in the main exchange to hold the line. She will then set up the connection to the party in the private automatic exchange who has asked her to establish the connection. lhc operation in the establishment of a local connection has already been described and will be readily understood. Vfhen the subscriber in the private automatic exchange answers the attendant is informed of this fact by the eliacernent of the supervisory lainp L whichoccurs upon the energization of the relay 179. It the subscriber in the private automatic exchange replaces his receiver before the called sul scr ber in the main office, the lay 179 is deenergized, the supervisory lainp L the local incoming connector such leased, and the trunk line freed for use before described, Should the called subscriber in the main exchange be the first to replace his receiver the normal current flow is again restored over the trunk linecoinprising conductors 140 and 141 and the electropolarized relay 177 'will be deenergized thereby lighting the supervisory lamp 2 to notify the operator that the called subscriber has replaced his receiverand opening the circuit of the slow acting relay 178 and closing the circuit of the relay 176. As before, relay 176 operates to establish a locking circuit for itself, tov remove ground from the When the called subscriber an-.

sleeve of the jack J and to disassociate the cord circuit from the trunk line. As there is now no bridge across the trunk conductors 1410 and 141 the operated switches in the main exchange are released in the usual manner and the two way trunk line is rendered accessible for calls in either direction in the same manner as before described. Another result of the energization of relay 176 is that the local connector switch which has been used to establish the connection to the party in the private automatic exchange is released in the same manner as has already been described. Upon noting the operation of the two su servisory lamps L and if the attendant operator will withdraw the plugs of the cord circuit 0 from the acks J and J; When the plug Preaches its normal aosition the plug seat switch PS is operated and the locking circuit 01" the relay l'fo of the cord circuit is opened. Upon (ls energizing, this relay opens the circuit of the sleeve relay 175 and restores certain other circuits in the cord circuit to normal.

it will nowbe convenient to d scribe certain features the trunk circuit coinprising conductors 140 and 1 11 interconnecting he and branch exchanges whereby it rte tiunlr line becomes either open or grounded it is automatically made busy at ooth ends and an alarm signal given to the exchange attendant in the main exchange. t will be noted that the energizing circuit .or the high resistance polarized relay 152 ncludes the line relay 123 or" the lineswitch C associated with the trunk line in the main exchange and also the right and left hand windings ot the shunt field relay 122. The construction of the relay 122 is similar to that of the relay 21 in the connector H already described. The relays 122 and 152 are energized over this circuit. However the line relay 123 reinains inoperative due to the high resistance of the polarized relay 152 and the shunting ei'lect ot the relay 122. New should the trunk circuit become opened relays 122 and 152 will deenergize. Relay 152 upon de neigizing closes the circuit ot the slow ac relay 153. The latter relay operates to place a busy potential upon the multiples of the trunk line in the banks of the local connector switches thereby preventing it being seized by a subscriber in the private automatic exchange. Relay 122 upon deenergizing opens the circuit of line relay 123 at its armature 145, and its armature 130 closes the circuit for the lower winding of he relay 12 1. It will be seen that the relay 12% is slow to energize but quick to deenergize as its upper winding is normally short circuited by armature 13S and its back contact. After a short interval relay 1241 energizes and, upon operating, establishes a locking circuit for itself at armature 133 to ground on common conductor 1 18, places ground upon the multiple test contacts such as 107 in the banks of the r0- tary connector switches and at armature 132 closes the circuit for an alarm in series with the lamp L to notify the attendant that one of the interconnecting trunk lines is in trouble. The lamp L is individual to the trunk lines extending to one private automatic exchange and serves to inform the attendant in what group 0t trunk lines to look for the trouble. When ground is placed on the conductor 120 the relay 121 is energized and operates to disconnect normal battery and ground and the windings of relay 122 from the trunk line conductors 1&0 and 14:1 for a purpose which will subsequently be made clear. WVhen the trouble is cleared the attendant will operate the common key K which opens the locking circuit oi the relay 12 1. Upon deenergizing, relay 12-1 removes ground from the multiple test contacts in the banks of the rotary connector switches. As the trunk line is now in good condition the relay 122 will now be energized to prepare the circuit of the line relay 123 and to open the circuit of the relay 124. If the trunk line should become grounded on either conductor the left hand coil of the relay 22 will be short circuited and this relay will be deenergized thereby opening a circuit of the line relay 123 so that it does not energize at this time at armature 145 and at armature 130 completes the circuit for the slow to operate relay 124. Since relay 122 is disconnected from both trunk conductors 140 and 141, in the manner previously described, current flow to the polarized relay 152 is cut oil regardless ofwhich trunk conductor is grounded and this relay therefore deenergizes to busy the trunk line to the local connector switches in the private branch eX- change in the same manner as it the trunk were open. Otherwise the operations are the same as have already been described.

Returning now to the connector 11 it will be remembered that when the connector switch automatically rotated until its wipers were associated with the last trunk line of the group and if this trunk line is idle the relay 2O energized. This relay operated to reverse the connections of the ring cut oil" and back bridge relay with respect to the switch wipers. The reason for this will now become apparent, inasmuch as the normal conductors extending from the line switch to the connector banks in the case of the last lines in a group are not. reversed as in rotary lines therefore the wipers of the connector switch must be connected in the opposite manner so as to properly operate the polarized relay 152 in the trunk circuits at the branch exchanges and the electro polarized relays 177 in the cord circuit. By the operation. of relay 20 this result is secured switch having a plurality 01'' sets of wipers,

trunk lines accessible thereto divided into groups and subgroups, directively controlled means for bringing the wipers of said switch into operative relation with one of said groups, directively controlled means for bringing said wipers into selective relation with one of said sub groups, means for causing said switch to test a plurality of trunk lines in said sub group simultaneously, a test relay associated with each set of wipers, another relay having two coils mounted upon different cores, a circuit for each coil of said relay controlled by said test relays, and means controlled by the energization of said other relay for causing said switch to test a plurality of other trunk lines in said sub group simultaneously.

2. In a telephone system, an automatic switch having a plurality of sets of wipers, bank contacts accessible to said sets of wipers, trunk lines divided into groups and sub groups terminating in said bank contacts, means for operating said switch into selective relation with one of said groups and then one-of said subgroups, a single test wiper for each set of wipers, meanscontrolled by said test wipers for causing said switch to test a plurality of trunk lines simultaneously, means for busying all the trunk lines in a subgroup, and means controlled by said test wipers for stopping the testing operations oitsaid switch when engagement is made with the bank contacts associated with the last trunk line in a subgroup regardless of its busy "or idle condition. g

3. In a telephone system, "an automatic switch, trunk lines of two classes accessible thereto, means for causing said switch to connect with atrunk line of either class, means for supplying current to the connected trunk line in one direction it the selected trunk line is of one class, and means operative if the selected trunk line is oi another class for supplying current in the opposite direction.

4. In a telephone system, an automatic switch, trunk lines of two classes accessible thereto, wipers for saidswitch, conductors in said switch, means for. operating said switch into connection with a trunk line in either class, means operative when connection is made with a trunk line of one class to]: earnest- 1 g said wipers to said conduth operative when connection is made with the trunk line of another class for connecting said wipers in an opposite manner to said conductors.

5. In a telephone system, an automatic switch, trunk lines divided into groups and sub-groups accessible thereto, directively controlled means for operating said switch into association with one or said groups and then into selective relation with one of said subgroups, automatic means then operative for causing said switch to select an idle trunk line in the selected subgroup, means operative when connection is made with an idle line in the selected subgroup controlled by a reversal of the two line conductors of said trunk line if said trunk line is not the last in the sub-group for applying a guard ing potential of one character to busy in trunk line, and means operative it said trunk line is the last of the selected subgroup and controlled by the normal connection of the two line conductors of said trunk line for applying a guarding potential of a diiierent character to busy said trunk line.

6. In a telephone system, an automatic switch, trunk lines divided into groups and sub-groups accessible thereto, directively controlled means for operating said switch into association with one of said groups and tors, and means then into selective relation with one of said sub-groups, automatic means then operative for causing said :switch to select an idle trunk line in the selected sub-group, means operative when connection is made with an idle line in the selected sub group controlled by a reversal of the two line conductors of said trunk line if said line is not the last of the sub-group for applying a guar ling potential of one character to busy said trunk line, means operative it said trunk line is the last of theselected sub-group and controlled by the normal connection of line conductors or" said trunk line for applying a guarding potential of a difierent character to busy said trunk line, another switch, means for operating said other switch into engagement with said trunk line, means in said other switch responsive to one of potentials for causingsaid other switch to test another line in the su group, and means in said other switch responsiveto the other of said potentials in case such potentialis connected to said trunk line for causing said other switch to stop its testing operation.

, 7. In a rotary connector having lines terminating in the banks of said connector and accessible thereto, test contacts for said lines, the line conductors of some of said lines being reversed with respect to the line con-,

reversal of the line conductors otthe line connected with for determining the value of the guarding potential to be applied to the test contact of the connected line.

8. In a telephone system, an automatic switch, a groupof lines accessible thereto, the line conductors of the last line in said group being reversed with respect to the other lines of said groups, test contacts for said lines, means in said switch effective when any line in said group except the last is connected with for applying a guarding potential of one character on the test contact thereof, and means in said switch controlled by the reversed line conductors when the last line of said group is connected with for applying a guarding potential or" a ditterent character.

9. In a telephone system, an automatic switch, a group' 031? lines accessible hereto, the line conductors of the last line in said group being reversed with respect to the other lines of said group, test contacts for said lines, means in said switch effective when any line in said group except the last is connected with for applying a guarding potential of one character on the test contact thereof, means in said switch controlled by the reversed line conductors when the last line of said group is connected with for applying a guarding potential of a diiierent character, a second automatic switch, means for operating said second switch into engagement with any one of said trunk lines, means in said second switch responsive to one of the guarding potentials in case the second switch is operated into engagement with the test contact having such i iotential thereon for causing said second switch to test another line in the group, and means in said second switch responsive to the other of said potentials in case the second switch is operated into engagement with the test contact having such other potential thereon for causing said second switch tostop its testing operations.

10. In a telephone system, an automatic switch, lines of two classes accessible thereto,

the line conductors of the lines of one class being reversed with respect to the line conductors of the lines of the other class, test cont-acts for said lines, means in said switch eiiective when a. non-reversed line'is connected with for placing a certain busy potential on the test contact thereoii, and means in.

trunk line with respect to the line conductors of the other lines of the group for determining whether an idle encountered trunk line is the last trunk line in the group.

12. In a telephone system, groups of trunk lines comprising rotary lines and non rotary lines, an automatic switch adapted when Operated to automatically rotate over all said rotary lines encountered ii busy but not said non-rotary lines, and automatic means in said. switch controlled by the line conductors of the rotary lines being reversed with respect to the line conductors of the nonrotary lines for determining whether an idle encountered one of said trunk lines of said groups is a rotary or a non-rotary trunk line.

13. In a rotary connector having lines of two classes accessible thereto, test contacts for said lines in the banks of connector, means for applying guarding potentials of one character on the test contacts of lines of one class when the same are connected with and found idle, and means controlled over a talking conductor of the lines of the other class for applying guarding potentials of a different character on the test contacts of lines of the other class when the same are connected with and found idle.

14. In a telephone system, an automatic switch having lines accessible thereto, a relay in said switch energized over a circuit including a wiper of said switch when said switch has been operated into connection with one of said lines, means in said switch for supplying talking battery to the C0111 nected line via the talking conductors of the switch, and means controlled by said relay for reversing the talking conductors of said switch with respect to the wipers of said switch.

15. In a telephone system, an automatic switch having lines accessible thereto, tworelays in said switch energized over circuits including separate wipers or said switch when said switch has been operated into con nection with one of said lines, means controlled by said first relay for connecting the talking conductors through to the wipers of said switch, and means controlled by said second relay for reversing the talking conductors of said switch with respect to the wipers of said switch and for completing a locking circuit for maintaining itself energized.

16. In a telephone system, an automatic switch having lines accessible thereto, a relay in said switch energized over a circuit including a talking conductor of one of said lines with which said switch has been ope ated into connection, and means controlled by said relay for reversing the talking conductors incoming to said switch with respect to the wipers of said switch.

17. In a telephone system, an automatic switchhaving lines accessible thereto, a relay in said switch energized over a circuit including a talking conductor of one of said lines with which said switch has been operated into connection therewith, means cone trolled by said relay for. reversing the talkconductors with respect to the wipers of said switch, anda locking circuit for maintaining said relay energized.

18. In a telephone system, a calling and a called line, means including an automatic switch for completing a connection between said lines, a test relay insaid switch operated during the establishment of said connection for controlling the automatic hunting movement of said switch, and means responsive to the replacement of the receiver by the called party for again operating said relay cause the release of said switch.

19. In a rotary connector switch, a test relay, means for operating said switch, means for operating said relayto control the huntoperation of said switch, and means for operating said relay tocause the re lease oi? the switch. I

20. In a rotary connector switch, a test relay for controlling the automatic hunting operation of said switch, a switching relay for completing theconnection to adesired line, and contacts on both of said relays for controlling the release of said switch.

21. In a telephone system, an automatic switch having a pair of testwipers, trunk lines accessible to said wipers, means for op erating said wipers step by step to engage said trunlr lines in pairs, and means in said switch for making a first and a second test of each engaged trunk line before said wipers are stepped to the neat pair of trunk lines.

22; In a telephone system, an automatic switch having a pair of test wipers, trunk lines accessible to said wipers, means for operating said wipers step by step to engage said trunk lines in pairs, and means in said switch for first consecutively testing the engaged pair of trunk lines and then in case said pair is busy, for simultaneously testing said pair before said wipers are stepped to the next pair of trunk lines.

23. In a telephone system, an automatic switch having a pair of test wipers, trunk lines accessible to said wipers, means for operating said wipers step by step to engage said trunk lines in pairs, means including a pair of test relays in said switch for consecutively testing a pair of said trunk lines, said relays energizedin case said pair of trunk lines are busy, and means including a third test relay in said switch controlled by said pair of relays for simultaneously testing the trunk lines of said pair.

24. In a telephone system, an automatic switch having a pair of test wipers, trunk lines accessible to said wipers, means for op erating .aid wipers step by step to engage said trunk lines in pairs, means including a pair of test relays in said switch for consecutively testing a pair of said trunk lines, said relays energized in case saic pair of trunk lines are busy, means including a third test relay in said switch controlled by said pair of relays for simultaneously testing the trunk lines of said pair, and means controlled by said third test relay for causing said first 10 means to. operate said wipers to engage another pair of trunks.

25. In a telephone system, an automatic switch having two test wipers, three test relays in said switch, means for energizing the 15 first or" said relays over a circuit including the first of said Wipers, means controlled by said first relay forclosing an energizing circuit through the second of said wipers for the second of said relays, means controlled by said second relay for closing an energizing circuit through both said'wipers for said third relay, and means controlled by said third relay for operating said switch.

26. In a telephone system, an automatic 2 switch, three test relays in said switch, means for energizing the first of said relays, means controlled by said first relay'for energizing the second or said relays, means controlled by said secondrelay for energizing said third 3e relay, and means controlled by said third relay for operating said switch.

' In witness whereof, I hereunto subscribe my name this 14th day of January, 'A. l). 1927'.

35 JOHN,E. GARDNER. 

